1. Field of the Invention
The present invention relates to an electric blind of vertical type and, more particularly, to an actuator for driving rotating rods borne in the casing frame of the electric blind (which may be either a vertical blind or curtain of electric type) with respective electric motors.
2. Description of the Prior Art
Representatives of the vertical blind according to the prior art are disclosed in U.S. Pat. Nos. 4,306,608 4,262,728 and 4,261,408, for example.
In these vertical blinds, generally speaking, two traverse and tilt rods for traversing and tilting slats are rotatably borne in the casing frame in juxtaposition to each other such that the traverse rod is rotated by its drive motor to traverse a plurality of runners reciprocally in the casing frame and such that the tilt rod is rotated by its drive motor to tilt the slats reciprocally, each of which is suspended from the corresponding one of the runners.
Incidentally, in the vertical blind of electric type, the traverse rod and the tilt rod are borne in the casing frame in parallel with each other such that the traverse rod has its one end connected through a drive transmission to its drive motor and such that the tilt rod has its other end connected through a drive transmission to its drive motor. Thus, in some actuator for actuating the vertical blind of the prior art, each of the rotating rods, i.e., the traverse rod or the tilt rod is given the driving force of the corresponding one of the motors at its one end.
In the prior art described above, either in case the slats suspended from the hooks of the runners are heavy or in case the rotating rods are long, the rotating rods require accordingly increased forces so that large-sized motors have to be mounted in the casing frame. As a result, the casing frame per se has to be enlarged in size, thus raising a problem that it is large-sized to have a rather ugly appearance.
Since a driving force is applied to one end of each rotating rod, moreover, in case the heavy slats are suspended, there arise a problem that a torsion is generated to twist the rotating rods or that the driving force fails to be completely transmitted to the other end of each rotating rod.
In the vertical blind, still moreover, the traverse rod and the tilt rod carry such supports as will be reciprocated by the rotations of the traverse rod so that the gap between the two rods and the gap between the two rods and the casing frame may be held constant to prevent the traverse rod from running out. For this purpose, the plural supports are reciprocated by the rotations of the traverse rod to keep the rod steady. As the vertical blind becomes the larger, the load to be applied to the runners becomes the higher to raise another problem that the traverse rod cannot be kept steady, varying from support to support.